Starter motor



Nov. 6, 1962 F. R. MERRIAM, JR

STARTER MOTOR 5 Sheets-Sheet 1 Filed March 14, 1960 u usu- IN VEN TOR.

R J M m m R W m KW. BY j xw A T TORNEKS Nov. 6, 1962 F. R. MERRIAM, JR 3,062,966

"sTARTER MOTOR Filed March 14, 1960 3 Sheets-$heet 2 FIG, 2

FRANK R. MERR/AM, JR.

11v VEN T0 R.

A T TORNEKS" Nov. 6, 1962 F. R. MERRIAM, JR 3,062,966

STARTER MOTOR Filed March 14, 1960 5 Sheets-Sheet 3 FIGS 7 o F/G4 FRANK RMERR/AMJR INVENTOR.

- 4 TTORNEKS United States Patent 3,062,966 STARTER MOTUR Frank R. Merriam, Jr., Plymouth, Mich, assignor to Ford Motor Company, Dearhorn, Mich., a corporation of Delaware Filed Mar. 14, 1960, Ser. No. 14,661 8 Claims. (Cl. 2% -38) This invention relates to an internal combustion engine starter motor and more particularly to a starter motor in which an electromagnetic means positioned adjacent one end of the starter motor simultaneously provides field excitation for the motor and a magnetic field for moving a pinion gear into engagement with an engine turning means.

The present invention provides an internal combustion engine starter motor in which a pair of movable pole pieces are operatively connected to a pinion gear. An electromagnetic means, preferably in the form of an annular field coil, is positioned at one end of the starter motor adjacent the pinion gear. The electromagnetic means, when energized, furnishes the field excitation for the motor and moves the movable pole pieces axially relative to the starter thereby moving the pinion gear into engagement with an engine turning means. Thus, there is provided a starter motor which employs a single electromagnetic means for furnishing the field excitation for motoring action, and for moving a pinion gear into en gagement with an engine turning means.

This invention provides advantages over prior art starter mechanisms which employ an electromagnetic means for moving a pinion gear into engagement with an engine turning means. Among the prior art are starter motors which employ the field windings to shift the whole armature in'a direction parallel to the armature shaft for moving a pinion gear into engagement with an engine turning means. In this type of starter motor a wide commutator must be employed since the armature shifts axially relative to the brushes or, as an alternative, some mechanism must be employed to move the brushes along with the armature. Furthermore, the armature presents a large mass which must be shifted axially and this requires a large magnetic field with a large number of ampere turns. Also, since the entire armature is moved the starter motor must be very sturdily constructed if it is to withstand the heavy shock loads which occur when the pinion gear fails to mesh properly with the engine turning means. The present invention eliminates these difficulties since only the movable pole pieces and the pinion gear are shifted when the starter is energized.

The invention also possesses advantages over other starter motors which employ electromagnetic means for engaging a starter motor pinion gear with an engine turning means. Many of these starter motors employ an electromagnetic means, other than field windings, for moving the pinion gear into engagement with an engine turning means and also employ a complicated system of levers for transferring the motion of a member actuated by this electromagnetic means to the pinion gear. Other starter motors employ the field windings to actuate lever mechanisms which move the pinion gear into engagement with an engine turning means.

The present invention, by utilizing one electromagnetic means for providing the field excitation for the motor, and for moving the pinion gear into engagement with an engine turning means, thus eliminates one of the electromagnetic means employed by certain of the starter motors mentioned above. Additionally, since the movable pole pieces are arranged to move axially of the starter motor, in the same direction that the pinion gear must be moved to engage an engine turning means, no complicated lever mechanisms need be employed.

An object of the present invention is the provision of a starter motor for an internal combustion engine which is relatively inexpensive and mechanically uncomplicated.

Another object of the invention is to provide a starter motor for an internal combustion engine in which an electromagnetic means is employed to furnish the field excitation for the motor and to move a pinion gear into engagement with an engine turning means.

Other objects and attendant advantages of the present invention will become more readily apparent as the specification is considered in connection with the attached drawings in which:

PEG. 1 is a sectional view partially in elevation taken along the lines 11 of FIG. 3;

PEG. 2 is a sectional view partially in elevation taken along the lines 2-2 of FIG. 3;

HS. 3 is a cross sectional view taken along the lines 3-3 of FIG. 2 with certain portions omitted for purposes of clarity, and

H6. 4 is a circuit diagram including the starter motor of the present invention.

Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown a starter motor 19 for an internal combustion engine. The starter motor is provided with a frame 11 constructed of a nonmagnetic material, for example, aluminum, which includes end plates 12 and 13. The two end plates may be constructed either of a magnetic or nonmagnetic material, and in the preferred embodiment of the invention these two end plates are constructed of a nonmagnetic material such as aluminum.

The end plates 12 and 13 carry bearings 14- and 15 respectively in which an armature shaft or power shaft 16 is rotatably mounted. Positioned upon the armature shaft are a commutator 17, a laminated armature core 18 and armature coils 19.

The armature or power shaft is provided with a helical splined portion positioned a short distance axially along the shaft from the end of the laminated core 18. A helical spiined barrel 21 is positioned over the splined portion of the armature shaft for engagement therewith. A driven means, preferably a pinion gear 22 adapted for engagement with an engine turning means 23, such as, a ring gear on a flywheel, is slidably mounted on the armature or power shaft 16 and is rotatably driven thereby. An overrunning clutch, the external portion of which is designated by the numeral 24, is positioned between the helical splined barrel 21 and the pinion gear 22. A spring member 25 aifixed to the end frame 13 engages the pinion gear 22 to bias it out of engagement with the engine turning means 23.

A pair of movable pole pieces designated by the numerals 26 and 27 are mounted within the frame 11 for axial movement relative to the armature or power shaft 16. As can best be seen by reference to FIG. 3, these movable pole pieces are positioned in channels 28 and 31 formed in the internal periphery of the frame by radially inwardly extending projections designated by the numerals 32, 33, 34 and 35. These projections extend axially of the frame for a distance sufiicient to guide the movable pole pieces over the entire extent of their travel. Each of the movable pole pieces 26 and 27 has a radially inwardly extending terminal portion designated by the numeral 36 (see FIG. 1). These terminal portions are alfixed to a collar 37 constructed of a nonmagnetic material, such as, aluminum or sintered copper, by means of pins, one of which is shown at 38.

The collar 37 includes a thickened end portion 41 having an internal diameter substantially equal to the external diameter of the armature or power shaft 16 so that the collar and the shaft engage each other in a sliding fit relationship. The mid-portion of the collar 37 engages the apes,

u) helical splined barrel 21 in a similar sliding fit relationship. The other end of the collar has an internal groove 42 positioned therein for the reception of coil spring 43 which is positioned about the helical splined barrel 21. A shoulder 44 formed by the groove 42 engages one end portion of the spring 43 while the external portion of overrunning clutch member 24 engages the other end of the spring.

A pair of fixed pole pieces 45 and 46 extend through slots 47 and 43 in the frame 11 and are affixed to a pair of frame covers 51 and 52 by screws 53 and 54. These frame covers are constructed of a magnetic material.

An electromagnetic means, such as, an annular field coil 55 in the form of a solenoid, is positioned in spaced relationship about the armature or power shaft 16 at the end of the frame adjacent the pinion gear 22 by means of a support member 56 constructed of a magnetic material. The support member 56 has a radially extending flange 57 which extends through a circumferential slot in the frame 11 into engagement with both of the frame covers 51 and 52 and is affixed thereto by means of screws, certain of which are designated by the numerals 58 and 59. The internal diameter of the support member 56 is substantially equal to the external diameter of the collar 37 so that the collar and the support member engage in a sliding fit relationship. An annular shoulder 61 on the support member 56 engages a shoulder 62 on the end frame 13. This together with the sliding fit engagement of the support member with the collar 37 properly positions the support member within the starter motor. The annular field coil 55 fits within a complementary annular groove 63 in the support member 56 and is affixed thereto by any suitable means (not shown).

The starter motor as shown on the attached drawings may be held together by a plurality of bolts positioned externally of the machine. These have not been illustrated since they are not pertinent to the novel features of the motor and since it is well within the skill of the routineer to provide them.

Referring now to FIG. 4 which shows a circuit diagram of the present invention, it will be seen that the starter motor is a series connected machine. The annular field coil 55 is connected through lead 71 to the brush 73 which engages commutator 17 and is connected through lead 72 to a starter motor switch 74. The starter motor switch is in turn connected to the positive terminal of battery 75. The negative terminal of the battery and the brush designated by the numeral 76 are grounded to complete the circuit.

When the starter motor switch 74 is closed, the annular field coil 55 is energized to provide the typical flux pattern of a solenoid. In the starter motor shown, the magnetic path for the flux extends from the center of the solenoid through the support member 56 including the radial extending flange 57 out to the frame covers 51 and 52. This flux path can best be seen by reference to FIG. 2. The flux path then extends to the fixed pole pieces 45 and 46 through the armature core 18 and the armature windings T9 to the movable pole pieces 26 and 27 (see FIG. 3). Since the frame 11 is constructed of a nonmagnetic material, such as aluminum, the fiux path from the fixed pole pieces to the movable pole pieces is through the armature and windings rather than through the frame. From" the movable pole pieces 26 and 27 the flux path extends through the air gap between the radially inwardly extending terminal portion 36 of each of the movable pole pieces and the support member 56 to the portion of the support member 56 positioned radially inwardly from the annual coil 55.

The magnetic field thus created causes the movable pole pieces 26 and 27 to move to the right, in FIGS. 1 and 2, to close the air gap between the terminal portions 36 of these movable pole pieces and the support member 56. This action moves the pinion gear 22 into engagement with the engine turning 23 by means of the 4 shoulder 44 of the collar 37 engaging the spring 43. The spring 43 cushions the shock load which may occur if the pinion gear 22 strikes the engine turning means 23 in a nonengaging position.

Prior to the time that the pinion gear 22 fully engages the engine turning means 23, the armature revolves slowly thereby slowly turning the pinion gear to aid its engagement with the engine turning means. As soon as full engagement is accomplished, however, the starter motor power shaft or armature shaft revolves at a high speed to drive the engine turning means 23. This action can readily be explained by reference to FIG. 1. It can be appreciated that the reluctance of the magnetic path described above is quite high prior to the full engagement of the pinion gear 22 with the engine turning means 23 because of the large air gap between the terminal ends 36 of the movabie pole pieces 26 and 27 and the support member 56. The density of the flux passing through the armature from the fixed pole pieces to the movable pole pieces, therefore, is quite small and the armature revolves at a relatively low speed. As soon as the pinion gear 22 fully engages the engine turning means 23, the terminal end portions 56 of the movable pole pieces 26 and 27 come into engagement with support member 56 and the air gap between them is reduced substantially to zero. At this time, the reluctance of the flux path is greatly reduced and the flux density in the armature is greatly increased. This causes the armature shaft to turn at the designed cranking speed.

It can be readily appreciated from the discussion given above that the electromagnetic means or annular field coil 55 simultaneously provides the field excitation for the motor and the magnetic field for moving the pinion gear 22 into engagement with the engine turning means 23.

It will be understood that the invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

I claim:

1. In an internal combustion engine, an engine turning means, a starter motor, said starter motor comprising a frame, a power shaft mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said power shaft, four pole pieces positioned about the periphery of said frame, two of said pole pieces being slidably mounted in said frame and operatively engaging said pinion gear, a field coil positioned in said frame in spaced relationship about the periphery of said power shaft at the end of said frame adjacent said pinion gear, said field coil when energized moving said slidably mounted pole pieces toward said engine turning means whereby said slidably mounted pole pieces move said pinion gear into engagement with said engine turning means.

2. In an internal combustion engine, a starter motor comprising a frame, an armature including an armature shaft rotatably mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said armature shaft, a plurality of pole pieces positioned around the periphery of said frame, one of said pole pieces being slidably mounted in said frame, means engaging said slidably mounted pole piece and said pinion gear, said pinion gear 'being adapted to engage an engine turning means positioned adjacent one end of said starter motor, and means positioned at the end of said starter motor adjacent said engine turning means for furnishing the field excitation for said motor and for moving said slidably mounted pole piece toward said engine turning means whereby said pinion gear moves into engagement with said engine turning means.

3. In a starter motor assembly, a starter motor frame, a power shaft mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said power shaft, a movable pole piece slidably mounted in said frame, said movable pole piece operatively engaging said pinion gear, and electromagnetic means positioned at the end of the starter motor frame for supplying the field flux for said starter motor and for slidably moving said movable pole piece and said pinion gear upon said shaft.

4. In a starter motor assembly, a starter motor frame, a power shaft mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said power shaft, a pair of movable pole pieces slidably mounted in said frame and upon said shaft for movement axially along said shaft, said pair of movable pole pieces having means in operative engagement therewith for engaging said pinion gear, and an annular field coil mounted at one end of said starter motor adjacent said pinion for supplying the field excitation for said starter motor and the magnetic field to move said movable pole pieces and said pinion gear axially upon said shaft.

5. In an internal combustion engine, the combination comprising an engine turning means, a starter motor for actuating said engine turning means, said starter motor including movable means for engaging said engine turning means, means movable axially of said starter motor engaging said movable means, and means positioned at the end of the starter motor adjacent said movable means and said engine turning means for providing the field excitation for said starter motor and for moving said means axially of said starter motor on said shaft whereby said movable means is brought into engagement with said engine turning means.

6. In an internal combustion engine, the combination comprising an engine turning means, a starter motor for actuating said engine turning means, said starter motor including a pinion gear movable axially of said starter motor for engaging said engine turning means, a pole piece movable axially of said starter motor and operatively engaging said pinion gear, and means positioned in said starter motor for furnishing the field excitation for said motor and for moving said pole piece and said pinion gear axially of said starter whereby said pinion gear moves into engagement with said engine turning means.

7. A starter motor for an internal combustion engine comprising, a starter motor frame constructed of a nonmagnetic material, a power shaft rotatably mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said power shaft, a plurality of pole pieces mounted about the periphery of said frame, two of said pole pieces being slidably mounted in said frame for axial movement along said power shaft and engaging said pinion gear, the remainder of said pole pieces being stationary with respect to said frame, an annular field coil mounted in said frame in spaced relationship to said power shaft at one end of said frame adjacent said pinion gear, means external to said frame for completing a magnetic circuit between said annular field winding and said stationary field pole pieces, and means internal of said frame for completing a magnetic circuit between said slidably mounted pole pieces and said annular field winding whereby said annular field winding provides the field excitation for said starter motor and moves said pinion gear axially upon said shaft by means of said slidably mounted pole pieces.

8. In a starter motor assembly, a starter motor frame, a power shaft mounted in said frame, a pinion gear slidably mounted upon and rotatably driven by said power shaft, slidable means movable axially relative to said power shaft mounted in said frame and engaging said pinion gear, and means positioned at the end of the starter motor frame adjacent said slidable means for providing field excitation for said starter motor and for slidably moving said slidable means and said pinion gear axially relative to said power shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,813,206 Jensen Nov. 12, 1957 

